84 GLOSSARY. 



Metapo'dium (Gr. meta, behind ; pom, podos, a foot). The 



posterior division of the foot in the Gasteropoda and 



Pteropoda. 

 Metapo'physis (Gr. meta, behind; apophuo, I sprout). The 



higher of two lateral processes sometimes developed on 



the arches of the vertebrae. 

 Meta/tery'gial (Gr. meta, behind; pterux, a wing). The 



hinder basal cartilage of the fin in the Elasmobranchii. 

 Metaster'num (Gr. meta, behind; sternon, the chest). The 



posterior portion of the sternum, sometimes termed the 



Xiphistemum, also the ensiform cartilage. 

 Metasto'ma (Gr. meta, behind; stoma, a mouth). A median 



elevation behind the mouth in the Arthropoda. 

 Metatar'sal (Gr. meta, beyond ; tarsos, sole of the foot). The 



name- given to each of the bones of the metatarsus. 

 Metatar'sus (Gr. meta, beyond; tarsos, sole of the foot). The 



portion of the pes or^foot which lies between the ankle 



and the toes. 

 Metatho'rax (Gr. meta, behind; thorax, a breastplate). The 



hinder segment of the thorax in the Insecta. 

 Metence'phalon (Gr. meta, behind ; enkephalon, the brain). 



The hind-brain, comprising the medulla oblongata and 



fourth ventricle. 

 Methaemoglo'bin. A substance obtained by the decomposition 



of hemoglobin. 

 Metos'teon (Gr. meta, behind; osteon, a bone). The posterior 



portion of the sternum in birds. 

 Micrococ'cus (Gr. mlkros, small ; kokkos, a kernel or berry). 



A minute organism allied to the Bacteria, having a bead- 

 like form. 

 Mi'cromere (Gr. mlkros, small; meros,& part). A term applied 



to the smaller of the two masses into which the vitellus of 



the Lamellibranch ovum divides in the course of develop- 

 ment. 

 Mi'cropyle (Gr. mlkros, small ; pule, a gate, entrance). A 



small opening left in some ova, by which the spermatozoa 



obtain access to the yolk ; also the opening in the ovule of 

 a plant through which the pollen-tube passes. 

 Micturition (L. micturlre, to desire to make water). The act 



of emptying the urinary bladder. 



Mid'riff (Sax. midd, middle ; hrif, the belly). The diaphragm. 

 Mi'nimus (L. the least). The fifth digit of the manus or of 



